The invention relates to a heddle frame construction for a loom of the type which includes a frame slat across the top and bottom of the heddle frame and heddle rods which may be attached to the frame slats between which heddles are carried in the frame. The bottom frame slat is connected to a heddle frame drive mechanism whereby the heddle frame is reciprocated up and down to create a shed in the warp yarns held in the central eyes of the heddles in which a weft yarn is inserted.
Due to the increasing speeds at which looms are operated and the increased dynamic forces encountered by the moving parts of the loom during high speed operation, the weight and structural integrity of these parts is a problem to which considerable attention must be given. In a heddle frame construction the heddle frame is driven by a heddle frame drive mechanism which typically includes hook connectors inserted within the hollow frame slat which hook upon a latch member fixed in the hollow frame slat. Not only must the bottom frame slat have sufficient structural strength to take the rigorous forces imparted by the drive mechanism, it must be sufficiently straight to prevent clashing against adjacent frames and binding of the heddles across the heddle rods.
Although the frame slat can be made stiffer by increasing the thickness of the outer walls and its height or weight, space limitations prevent this. The bottom frame slat must of necessity have a narrow dimension to accommodate the use of multiple heddle frames in close proximity to one another. Typically, the bottom frame slat must be no thicker than ten millimeters and the side walls of the hollow body slat no thicker than two millimeters to accommodate the space available on the loom. Thus, to meet the load requirements, frame slats typically have been constructed from high strength steel material. However, this adds considerable weight to the heddle frame structure.
Since the drive motion is normally not imparted to the top frame slat it is an object of the present invention to provide a top frame slat having a different construction than a hollow steel frame slat used for driving the heddle frame on the bottom so that the overall weight of the frame may be reduced without sacrificing structural integrity for high speed operation.
Swiss Pat. No. 464,112 discloses a frame slat for a loom constructed of a sheet metal or stainless steel tubular member which is formed to include hook ends for retaining heddles. However, it has been found that such shapes which are formed and heat treated often include dimensional and shape variances which are outside the acceptable tolerances for heddle frame constructions.
Typical heddle frame constructions including frame slats with integral slat beams and heddle rod supports are disclosed in U.S. Pat. Nos. 3,970,114, 3,754,577, 2,697,454, and Dutch Pat. No. 2,427,573.
Accordingly, an important object of the present invention is to provide a heddle frame having a tubular steel bottom frame slat by which the heddle frame is driven and a composite top frame slat which is of a lighter construction to provide a lighter overall heddle frame construction for high speed operation.
Still another important object of the present invention is to provide a frame slat for a heddle frame having a composite construction which combines the advantages of a steel construction in those areas of the frame slat where strength is required and which includes lightweight extruded constructions in other portions of the frame slat where the structural properties of steel are not required.
Still another important object of the present invention is to provide a frame slat for a heddle frame having a composite construction providing a lightweight frame slat for use on high speed looms.